Method of furnace operation



United States Patent 3,212,554 METHOD OF FURNACE OPERATION Emil Blaha, Cheltenham, Pa., assignor to Selas Corporation of America, Dresher, Pa., a corporation of Pennsylvania Filed Apr. 18, 1961, Ser. No. 103,848 Claims. (Cl. 158--7.6)

The present invention relates to furnaces, and more particularly to a method of operating a furnace so that the products of combustion are used to preheat the air as it is being supplied to the burners.

For reasons of economy, it is desirable to preheat the air used for combustion in furnaces. This is usually accomplished by recuperation or regeneration, wherein all the air used for multiple burners in a furnace is heated at one time and in one place. This heated air is then piped in suitably insulated ducts to individual burners located at various places in a furnace. Such an arrangement requires a large amount of piping that is expensive and requires an excessive amount of room in a congested area.

It is an object of the present invention to provide a method of operating a furnace so that the products of combustion are used to preheat air for each burner directly and individually.

It is a further object of the invention to provide a method of supplying preheated air to each burner of a multiple burner furnace, with the preheating taking place at the burner.

In practicing the invention, the furnace is provided with a plurality of openings adjacent to each burner, through which products of combustion can be exhausted. As the gases flow through these openings, they pass in heat exchange relation to the combustion air flowing to the burners to heat it. The flow of combustion gases and therefore the amount of preheat can be regulated by regulating the furnace pressure.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages .and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a section through a furnace that can be operated in accordance with the invention,

FIG. 2 is a section through a burner in the furnace Wall,

FIG. 3 is the front view of a burner taken from the right in FIG. 2, and

FIG. 4 shows a modified form of apparatus that can be used in practicing the invention.

Referring to the drawings, there is shown in FIG. 1 a furnace 1 that can be built in accordance with ordinary furnace construction. The furnace is provided with a chamber 2 in which Work is to be heated, and is provided with a stack through which products of combustion are exhausted. The stack is provided with a damper 4 that can be adjusted either manually or automatically in order to keep the furnace pressure at the desired value. A conventional support 5 is shown in the bottom of the furnace, upon which work to be heated is placed. At least one wall of the furnace has in it a plurality of burners 7 which can be of any desired type if they have or can be provided with the individual recuperative features that are required by the invention.

Referring to FIG. 2, the wall of the furnace is shown as having inserted in it a burner block B consisting of two ceramic parts, cemented together, including a first part 8 which may be square, as shown, and a second part 9 having a cup 10 formed in the face thereof. The block is built into and flush with the furnace wall, with the cup opening into the furnace chamber. The base of the cup has a recess 11 in it. The two parts of the block are formed separately for convenience, with the second part 9 having projections and recesses around its outer edge, so that a plurality of passages 12 extending backwardly from the furnace chamber wall will be formed when the blocks are assembled. These passages terminate at their rear ends in a cylindrical recess 13 in the furnace wall that extends to the left in FIG. 2 to the exterior of the furnace. A passage 14 extends axially from the base of the recess 11 to the recess 13.

A cylindrical burner body 15 of heat transmitting material, such as metal, is received in the recess 13. The central portion 16 of this body extends forwardly from the base to a front wall 17 that engages the back of the burner block. The shape of front wall 17 holds the burner body axially disposed in recess 13 at its front end, while the rear end of the burner body is positioned axially in the recess 13 and held in place in wall 6 by a bracket 18 having a portion engaging the outside of the furnace wall, and an axial opening which receives a rearwardly extending portion of the burner body. This rearwardly extending portion is indicated at 19 and forms the air inlet through which air for combustion is supplied to the burner.

A gas distributor 21 extends through the wall 17 and is received in the axial opening 14. This gas distributor is hollow and has a ring of gas discharge openings 22 drilled in a chamfered portion on its front end. Member 21 is held snugly in opening 14 by a plurality of helical ribs 23 which are formed on its outer surface. Gas is supplied to the rear end of member 21 through an axially extending gas pipe 24 that projects radially from air pipe 19. An air path is provided from the supply 19 between the inner periphery of central portion 16 of the burner body and a refractory cylinder 25 that is held on the axially extending portion of pipe 24. This cylinder is made of refractory primarily to prevent heat transmission through it to the gas supply pipe. It is noted that the cylindrical portion 16 of the burner body is spaced from cylinder 25 to form the air passages, and is spaced from the wall of recess 13 to provide a passage 27 through which products of combustion can be exhausted from the furnace. In order to increase the heat transfer between the air fiowing to the furnace and the products of combustion flowing from the furnace, wall 16 is provided with internal fins 28 and external fins 29.

In operating the furnace according to the present invention, fuel and air are supplied respectively through pipes 24 and 19 to the burner. The air passes around cylinder 25, and as it is discharged, is directed by ribs 23 in a helical path, so that it will move radially outwardly along the surface of cup 9 into the furnace chamber. Gas flows through openings 22, and is drawn, partly by the action desired burning rate.

of the air, radially outwardly to mix with this air, so that the fuel mixture will burn along the surface of cup 9 to heat that surface to incandescence. Radiant heat is therefore directed into the furnace chamber to heat the work contained therein. The products of combustion circulate in the furnace chamber and help heat the charge by convention. The fuel and air may be supplied in any desired proportions for the type of atmosphere that is required for the heating job being performed. The fuel and air can also be supplied under suitable pressures to get the These products of combustion are normally discharged through one or more stacks to the atmosphere. By closing damper 4 the furnace pressure can be increased, thereby causing some of the products of combustion to be exhausted through passages 12 surrounding each of the burner cups. The hot products of combustion flowing from the furnace through these passages will pass around burner body 16 and through heat exchange will heat the air being supplied to the burner. If the products of combustion are in the neighborhood of 2000, about 700 preheat can be obtained for the inflowing air. The amount of preheat that can be obtained will, of course, depend upon the amount of the products of combustion that are discharged through the openings 12. This can be adjusted by varying the damper 4. As the damper is closed, more of the products of combustion will have to escape through passages 12, and thereby will increase the heat transfer to the incoming air.

In the arrangement described above, substantially the same amount of products of combustion will be discharged through openings 12 around each burner. Therefore the preheat for each burner will be substantially the same, thus producing an even temperature in the furnace chamber. In some cases, however, it may be desirable to have pattern heating in the furnace, in which a particular portion of the furnace or work being heated is at a higher temperature than other portions. This can be accomplished by having the burners directed toward that portion of the furnace or work at a higher temperature than the others. The temperature produced by any burner can be varied by varying the preheat of the air supplied thereto as well as in varying the fuel.

In FIG. 4 there is shown apparatus for varying individually the amount of products of combustion that can be withdrawn from around or through each burner, Referring to that figure, it will be seen that instead of exhausting to the atmosphere from passage 27, the products of combustion are received in a chamber 31 attached to the rear of the furnace. The outer wall of this chamber serves to hold the burner body in place and centered in recess 13. Chamber 31 is provided with a stack 32 that has centered in it a nozzle 33 directed toward the exit of the stack. Air or other gas under pressure is supplied to nozzle 33 from a pipe 34 having a valve 35 therein.

In following the method of the invention with apparatus of this type, the preheat of the air to the burners can be varied by the adjustment of damper 4 as was previously described. In addition to, or in lieu of the use of the damper, various amounts of combustion gases can be drawn from around each burner by gas flowing through nozzle 33. As valve 35 is adjusted, more or less combustion gases will be aspirated through stack 32. The more gas flowing through each stack 32, the higher the air supplied to that burner will be preheated, and the more heat will be given by the burner. Thus the heat of the furnace can be patterned by varying the heat of the individual burners.

From the above it will be seen that I have provided a method for operating a furnace in which the air supplied to each burner is preheated individually as this air is flowing through the furnace wall to be burned in the furnace.

'The amount of preheat can be determined by a simple An arrangement of this type utilizes a large portion of the heat that would otherwise be exhausted through the stack and wasted. Furthermore, by having the air preheated individually in each burner as it is moving toward the furnace, the necessity for recuperators and the large amount of piping that would be needed with such an arrangement is completely done away with. The method of the invention herein is a simple and effective way of controlling the preheat of the air to each burner individually in response to furnace pressure.

While in accordance with the provisions of the Statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit and scope of the invention set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

What is claimed is:

1. The method of operating a furnace having a chamber, walls surrounding the chamber, a stack leading from the chamber and a plurality of separated burners in the walls which comprises supplying fuel and air to the chamber through each burner individually and burning the fuel and air along said Walls adjacent to each burner to heat said walls to incandescence, discharging the products of combustion produced by said burning into the furnace chamber, removing a portion of the products of combustion from the chamber through the stack, removing the remainder of said products of combustion from the chamber through the walls at a plurality of separated locations with each location being adjacent to a separate burner, and passing the products of combustion leaving each location in heat exchange relation in said walls with the air supplied to the burner adjacent to that location thereby to preheat individually the air supplied to each burner.

2. The method of claim 1 including the step of controlling the furnace pressure and thereby controlling the volume of products of combustion removed through said locations.

3. The method of claim 1 including the step of controlling individually the quantity of products of combustion removed from the location surrounding each burner thereby individually to control the amount of preheat of the air supplied to each burner.

4. The method of operating a furnace having a plurality of separate burners located at spaced points on its inner wall and in which the burners are provided with separate means through which fuel and air are supplied to the furnace chamber which comprises supplying fuel and air through each of the burners, burning the fuel and air from each burner along portions of the surface of said inner wall adjacent to the burner to heat the wall to incandescence and thereby radiate heat to the furnace, discharging the products of combustion produced by said burning into the furnace chamber, removing a portion of the products of combustion from the furnace chamber through the wall at groups of locations adjacent to and surrounding each separated burner, and using the so removed products of combustion from each group of locations to preheat the air supplied individually to the burner adjacent to each group of locations.

5. The method of operating a furnace having a chamber surrounded by walls, a stack for exhausting products of combustion and a plurality of separated burners in one or more of said walls which comprises supplying fuel and air through the burners separately, burning the fuel and air in the chamber adjacent to each burner in the wall in which the burners are located to heat the chamber, discharging the products of combustion produced by said burning into the chamber, removing a portion of the products of combustion from the chamber through the walls from a plurality of locations adjacent to and surrounding each separated burner, passing said products of 5 6 combustion in heat exchange relation with the air sup- 1,826,213 10/31 Hepburn 15836 X plied to the individual burners while they are flowing 2,188,133 1/40 Hepburn 1587.6 X through the wall, and varying the amount of preheat of 2,547,735 4/51 Blaha 158-99 X the air for each burner by individually varying the volume 2,855,033 10/58 Furczyk 15 8109 of products of combustion exhausted through each of said 5 2,918,117 12/59 Grifiin 1581 1 It f 1 t P 1 y Ions FOREIGN PATENTS References Cited by the Examiner 719,944 4/42 Germany UNITED STATES PATENTS Prlmaly Exdmmr.

871,070 11/07 Schwartz 1587.6 X FREDERICK KETTERER, ALDEN D. STEWART,

1,724,783 8/29 Smallwood et al 15836 PERCY L. PATRICK, Examiners. 

1. THE METHOD OF OPERATING A FURNACE HAVING A CHAMBER, WALLS SURROUNDING THE CHAMBER, A STACK LEADING FROM THE CHAMBER AND A PLURALITY OF SEPARATED BURNERS IN THE WALLS WHICH COMPRISES SUPPLYING FUEL AND AIR TO THE CHAMBER THROUGH EACH BURNER INDIVIDUALLY AND BURNING THE FUEL AND AIR ALONG SAID WALLS ADJACENT TO EACH BURNER TO HEAT SAID WALLS TO INCANDESCENCE, DISCHARGING THE PRODUCTS OF COMBUSTION PRODUCED BY SAID BURNING INTO THE FURNACE CHAMBER, REMOVING A PORTION OF THE PRODUCTS OF COMBUSTION FROM THE CHAMBER THROUGH THE STACK, REMOVING THE REMAINDER OF SAID PRODUCTS OF COMBUSTION 